Lotus Elan

Fanbelts pullys and waterpumps

PostPost by: Concrete-crusher » Sun Jun 18, 2017 5:59 pm

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My dynamo pully has failed today after what is only a few hundred miles from new. I understand not to overtighten it and although possible don't think it was too tight.

Looking at the pully the fan belt does not sit at the bottom meaning and load will create a lateral force is this normal or do I have the wrong pully

My second question for those who know , the water evaporated in the engine forcing its way out into the expansion chamber , I guess I drove about 2 miles with the broken pully , would this damage the water pump as I can hear a sqeek if I turn it by hand , it may have always squeeked but been covered by the engine noise

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PostPost by: RogerFrench » Sun Jun 18, 2017 6:27 pm

Fan belts run in the vees of pulleys, and are driven, or drive, by their flanks. They should not sit right down if they are of the correct profile.
I would not have thought a couple of miles would have been enough to damage the pump, but if it squeaks, I could be wrong.
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PostPost by: richardcox_lotus » Sun Jun 18, 2017 7:02 pm

I don't believe my fan belt is ridged like that

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PostPost by: Elanman99 » Sun Jun 18, 2017 7:09 pm

My first thought when I saw the picture was that I had never seen a twink with a cast iron pulley on a dynamo (alternator?). I now realise it probably a moulded plastic pulley you have fitted rather than the usual pressed steel type.

The plastic material should be capable of withstanding the belt tension but maybe yours had been knocked at sometime in the past and got a crack that spread.

I mentioned alternator above, because although its not easy to tell from a photograph, the pulley diameter looks very small for the dynamo which does run slower.

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PostPost by: MarkDa » Tue Jun 20, 2017 6:12 am

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PostPost by: vxah » Tue Jun 20, 2017 7:11 am

The toothed looking belt is just a more modern type of "v" belt, the grooves allow it to curve around a pulley easier without too much loss of surface (grip) area.
I was thinking could it have been excess heat that caused the pulley failure? If the belt is too slack and slippage takes place a lot of heat can be generated at the pulley, Although that said a dynamo does not really put that much load on the belt due to it's low output... Unless it's faulty? Or the pulley is a replacement from a spurious manufacturer?
I would not worry yet about a little squeak from the water pump when turned by hand as it's not unusual for pumps to do that as the seal parts are moving quite slowly against each other, get some proper rpm's on it and see? Unless there is a load of play in the bearings?
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